Achiote or Annatto seeds is a spice that grows heavily in the Yucatán area and is unique and native to this area. The seeds come from the Annatto tree, which grows beautiful pink flowers that produce a prickly pod which has dozens and dozens of these seeds inside (continue for more information and photo).

The seeds have a beautiful brown, brick, reddish warm and appealing
color. The Mayas used the seeds since Pre-Hispanic times to color their
skin, garments, art and they also mixed them with their chocolate drink
as a symbol of blood, given the color, in their rites. The seeds
provide a strong, pungent and sort of permanent flavor to the dishes
they are used in.